Every pastelist (and many others) face this dilemma on a regular basis. There are two trains of thought when it comes to blending in pastels-
"It dulls the color" When you blend pastels, it breaks down the crystalline edges of the layers of the pigment and combines them. Sort of like mixing paint on a palette. This process makes the color less pure and vibrant.
"Creates soft edges" Opposite school of thought is that blending creates soft passages and "lost edges" in a painting which furthers the illusion of depth and space.
I learned to paint with oils, not pastels, so blending is part of my vocabulary. I recently received some feedback from a famous pastelist friend who said my works "looks too much like oil," because of the blending.
If you blend, you create soft passages through the painting that may soften the stroke and disguise the medium. Also, you have to use your hand. There are other blending tools, but hands are easiest and most accessible. When you touch pastel, you are touching a toxic substance.
Many pastelists don't want to imbibe toxins through the permeable skin on your fingers. I'm one of them, so I use a barrier called Liquid Gloves that you get at hardware stores. This protects your skin from paint and pastel. It also makes your hands easier to wash and get clean-not that mine are ever truly clean!
Pastelists who don't blend with their fingers, use the side of the stick, or feathering-lots of little strokes to blend. This leaves the color pure and distinct. There is also a rule in pastel where the last layer you apply is the first layer that hits the eye. So you want to save your pop color for the last layers.
Below is an example of blending and not blending in the same painting. If you look at the background areas; pump house and tree line, they are all blended and soft. This creates an illusion of depth and distance.
In the middle ground water, there are side strokes of pastel that are unblended, on top of blended blocks of color. This is a combination of both techniques.
In the foreground, the Aningha and the grasses are all clean lines of feathered pastel strokes. These are crisp layers of color that sit on top of each other. This gives texture and a feel of mark-making to the painting. It also gives sharp edges that makes the foreground come forward.
To blend or not to blend is a personal artistic choice. It may not be fashionable in the pastel world today to blend, but don't let fashion dictate your style. Instead, listen to that inner muse and paint what and how spirit moves you to paint.
Looking forward to seeing what you paint!